The existing overheat protection control means (also called boil-dry protection control means) for liquid heating vessels are mostly used and mounted under the bases of liquid heating vessels, especially water boiling vessels, wherein the base of said vessel is provided with an electrical heating element. There are mainly two types of such overheat protection control means: one type provided with only one thermally sensitive bimetallic actuator, and the other type provided with two thermally sensitive bimetallic actuators. Because the first type has only one actuator, if it goes wrong or fails to operate, the heating vessel is easy to boil dry and overheat and then be burned out. On the other hand, because the two actuators of the second type are made of different materials, the two actuators will operate at different temperatures. Wherein the actuator operable at a higher temperature will produce an actuating movement when the temperature of the heating vessel is too high, that results in overheating and burning out the heating vessel; while the actuator operable at a lower temperature is easy to produce an actuating movement when the temperature of the heating vessel is not high, that results in influencing the normal use of the heater.